Apparatus for producing cyanogen chloride by spray reaction means

ABSTRACT

Apparatus for producing cyanogen chloride has a vaporizer in which hydrogen cyanide and chlorine are mixed to produce a gaseous mixture. A spray chamber is provided in which the gaseous mixture is dispersed, and means are provided for spraying water into the spray chamber, the amount of water being controlled so that the resulting hydrochloric acid is at a concentration of about 10 percent. If necessary to complete the reaction, a cooled reactor can be provided into which the cyanogen chloride, unreacted hydrogen cyanide vapor and chlorine are passed. The reactor should be partially flooded with hydrochloric acid at a concentration of about 10-20 percent and chlorine stripped from the hydrochloric acid produced in the spray chamber is also fed to the reaction column.

Unite States Suryanarayana et a1.

1451 Mar. 27, 1973 54 APPARATUS FOR PRODUCING 2,377,781 6/1945 Hebbard..261/148 CYANOGEN CHLORIDE BY SPRAY 5 ,213; 6/13?S Heuser.,... ,775,12/1 Rupp REACTION MEANS 2,701,184 2/1955 Rupp [75] Inventors:Yelogondahally Subrananiam Su- 2,524,341 10/1950 Chapman et a1. ..23/119ryanarayana; William sandford 2,468,365 5/1949 Campobasso et al ..26l/l17 X Durrell, both of Mobile, Ala. Primary Examiner-James H. Tayman, Jr.[73] Ass1gnee: Ciba-Gelgy Corporation, Ardsley, Att0mey wenderoth' Lind& Ponack NY. 22 Filed: Dec. 30, 1969 1 ABSTRACT [21] Appl. No.: 1,908Apparatus for producing cyanogen chloride has a vaporizer m whichhydrogen cyanide and chlorine are Related U.S. Application Data mixed toproduce a gaseous mixture. A spray chamber 62 M h l 967 P is provided inwhich the gaseous mixture is dispersed, 1 g g iggggf are 1 and means areprovided for spraying water into the spray chamber, the amount of waterbeing controlled so that the resulting hydrochloric acid is at a concen-[52] tration of about 10 percent. If necessary to complete 3/3 l 4 4 thereaction, a cooled reactor can be provided into 261/ 261/1 9 which thecyanogen chloride, unreacted hydrogen cyanide vapor chlorine are passedThe reactor [58] held of Search 283; should be partially flooded withhydrochloric acid at a 26mm 148; concentration of about 10-20 percentand chlorine 196/127 128; 259/4 stripped from the hydrochloric acidproduced in the spray chamber is also fed to the reaction column. [56]References Cited 1 Claim, 2 Drawing Figures UNITED STATES PATENTS1,414,762 5/1922 Townsend ..23/26O X cNcl+c|2 VWLAAA 38 1 H2O km 7 29 so3 l 0,, 32 i G :flmfiwlp Q SEMR LUM 3? HC (10 COLUMN 27 271 l m a 37 4-W n1 H SPRAY 5 A 25 CHAMBER 2s CHAMBER z iv HCN Q APPARATUS FORPRODUCING CYANOGEN CHLORIDE BY SPRAY REACTION MEANS This application isa division of our copending application Ser. No. 622,332, filed Mar. 10,1967, now US. Pat. No. 3,498,761.

BACKGROUND OF THE INVENTION 1. Field of the Invention This inventionrelates to a method and apparatus for the production of cyanogenchloride, and more par ticularly it relates to the production ofcyanogen chloride by spraying water into a gaseous mixture of hydrogencyanide and chlorine whereby the by-product acid is at relatively highconcentration.

Cyanogen chloride is a valuable intermediate for the production ofcyanuric chloride, which in turn is useful as an intermediate for themanufacture of many products, such as chemotherapeutic agents,herbicides, dyes, brightening agents, synthetic resins, plastics,rubber, explosives and other materials.

2. Description of the Prior Art A presently used commercial process ofpreparing cyanogen chloride for conversion into cyanuric chloride isdescribed in US. Pat. No. 3.l97,273 in the name of Elwood Bruce Trickey.In this process, chlorine and hydrogen cyanide are charged into thereaction section of a packed column having a purification, washing orscrubbing section, a reaction section, and a stripping section. Water isfed in at the top of the scrubbing section and steam is introduced atthe base of the column at the bottom of the stripping section. Bymaintaining the proper rates of feed of the various materials, thetemperature and conditions in the column can be maintained such that ahigh yield of cyanogen chloride is obtained as a gas at the top of thereactor.

The process of this patent, while it is quite satisfactory with respectto the quality and amount of the product which it is desired to produce,also produces at the bottom of the reactor column a by-product ofdilute, i.e., 2-3 percent aqueous hydrochloric acid. This by-product isrelatively easily disposed of when the quantity thereof is small, but inactual practice the amounts produced are so great that they cannot bedisposed of simply by discharging into a stream or river withoutexceeding the amount which can be so discharged as established bypollution control standards. The alternative of concentrating the dilutehydrochloric acid and using it in other processes or selling it is noteconomically feasible, since the costs of concentrating the dilute acidare greater than purchasing concentrated acid from commercial sources.

Production of the cyanogen chloride under conditions which would producethe by-product aqueous hydrochloric acid at higher concentrations haveheretofore appeared to be an unlikely solution to the problems ofby-product disposal or lay-product recovery, because of the twinproblems of intolerable, from the commercial standpoint, losses of theproduct cyanogen chloride by hydrolysis and directly from the bottom ofthe reaction column along with the byproduct hydrochloric acid. Thenecessity to keep hydrolysis losses low and substantially eliminate lossof cyanogen chloride are essential to the successful commercialproduction of cyanogen chloride. A third essential condition is theprevention of the formation of NCL which is extremely explosive andtherefore an undesired reaction product not only from the standpoint ofloss of the primary product but also from the standpoint of safety.

SUMMARY OF THE INVENTION The present invention relates to an apparatusfor overcoming the problems described above and carrying out thereaction of chlorine and hydrogen cyanide to produce cyanogen chlorideby feeding the two raw materials as a gaseous mixture into a spraychamber and spraying water into the spray chamber. By carefullycontrolling the conditions, a high rate of conversion to cyanogenchloride can be achieved at low hydrolysis losses and production ofaqueous hydrochloric acid in concentrations up to about 10 percent. Thereaction can be carried nearer to completion by passing the strippedbottoms from the spray chamber in countercurrent flow to the gaseousoutput from the spray chamber, and the bottoms from such a reactionapparatus will be near 20 percent hydrochloric acid.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be described inconnection with the accompanying drawings, in which:

FIG. 1 is a schematic view of an experimental apparatus including aspray chamber arranged to carry out the novel steps of the method of thepresent invention; and

FIG. 2 is a schematic view of a practical apparatus for carrying out themethod of the present invention.

DESCRIPTION OF PREFERRED EMBODIMENTS As shown in FIG. 1, an experimentalapparatus according to the present invention comprises a vaporizer 10having a liquid hydrogen cyanide inlet 11 and a gaseous chlorine inlet12. By application of external heatthe liquid HCN is vaporized in thevaporizer. The outlet 13 from the vaporizer is connected to a gas.dispersing head 14 in a spray chamber 15 into which extends a waterinlet 16 having a spray nozzle 17 on the end thereof. Gaseous reactionproducts leave the spray chamber through a gas outlet 18 and liquidreaction products leave the spray chamber through the liquid outlet 19.

In operation, liquid I-ICN is pumped into the vaporizer l0 and gaseouschlorine at ambient temperature is pumped into the vaporizer and the HCNis vaporized and mixed with the chlorine. The resulting mixture isdispersed into the spray chamber 15 through the gas dispersing head 14and water is sprayed into the gaseous mixture through the nozzle 17 in aspray of very fine droplets. The reaction goes nearly to comple tion inthe spray chamber, and the gaseous cyanogen chloride mixed withunreacted I-ICN and chlorine passes off through the gas outlet 18 whileaqueous hydrochloric acid in concentrations up to 10 percent is removedfrom the bottom of the spray chamber.

The amounts of chlorine, I-ICN and water are controlled so that thereaction produces aqueous hydrochloric acid as a by-product inconcentration of about 10 percent.

A specific example will be given in order to show the manner ofoperating the apparatus according to the invention.

EXAMPLES 1 and 2 Liquid HCN was fed to the vaporizer, and chlorine wasfed into the vaporizer at ambient temperature and in an amountsufficient to give an excess of percent over that needed for completereaction with the HCN. The resulting vapor, which was a mixture of HCNand chlorine, was dispersed into a spray chamber which was 9 inches indiameter and 18 inches high. Water was sprayed into the chamber fromabove in a spray of fine droplets. The'amounts of HCN and water aregiven below in runs 1 and 2 in Table 1. The resulting gaseous productwas dried and the amount of CNCl contained therein measured. Theconcentration of the liquid acid which remained in the bottom of thespray chamber was also measured.

As can be seen from the Table, the conversion rates for the two runswere in the neighborhood of 75 percent, and the concentration of theacid was found to be near 10 percent.

A practical embodiment of the apparatus for manufacturing cyanuricchloride using the spray chamber apparatus and method described above isseen in FIG. 2. The apparatus comprises a vaporizer 20 in the form of aheat exchanger 6 feet long and having 199 tubes with a /s-inch diameter.Liquid HCN is fed into the vaporizer through an HCN inlet 21, and partof the chlorine is fed into the vaporizer through a chlorine inlet 22.The remainder of the chlorine is by-passed through a by-pass line 24which joins the vapor line from the vapor outlet 23 from the vaporizer.

Two spray chambers 25 are provided, each of which is feet wide and feethigh, and made of stoneware. Each chamber has five nozzles 26 thereinwhich are fixed to an 8 foot diameter ring 27 placed at the center ofthe top of the chamber. A gas dispersion means 28 is positioned in thebottom of each chamber on the end of the HCN-chlorine feed line. A watersupply pipe 29 leads to each set of water spray nozzles 27 Each spraychamber has a gas outlet near the top thereof from which a gas line 30extends to a separator 31 for separating liquid from the gas, and fromthe separator 31 a line leads to each of two 30 inch diameter packedcolumns 32 having a heat exchanger in the middle thereof. The columns 31each have an upper packed section 12 feet long and a lower packedsection 9 feet long, both sections being packed with ,-inch saddles. Theheat exchanger section is 9 feet long and has 109 l inch tubes therein.The outlet line from the separator 31 enters each of the packed columnsjust below the heat exchanger section.

Each spray chamber also has a liquid outlet near the bottom thereof fromwhich the liquid line 33 leads to a reboiler 34. The reboiler issupplied with steam by lines (not shown) and heats the bottoms from thespray chambers 25 to drive off the chlorine therefrom, and a chlorineline 35 extends from the reboiler to the line between the se arator 31and the packed columns 32. An HCl line ex ends from the reboiler througha pump 36 and a cooler 37 and branches to the top of each of the columns32.

A gas outlet line 38 is provided at the top of each column 32, and abottom line 39 leads from the bottom into said spray chamber, waternozzle means directed of each column 32 to a second reboiler 40, whichis also steam heated by a steamsupply (not shown). The chlorine linefrom the second reboiler leads back into the lower packed section ofeach column-32, and an acid line from the bottom of the second reboiler.

It is contemplated that by feeding 1,605 lbs./hr. HCN and vaporizing itwith 1,841 lbs/hr. chlorine, and bypassing about 3,445 lbs/hr. of thechlorine, and by spraying water into the spray chambers at a rate of5,286 lbs./hr., the apparatus can produce 3,660 lbs/hr. CNCl. Underthese conditions, the cooling water should enter the heat exchanger partof the columns 32 at about 25 C and leave at 28 C, and the temperatureof the liquid at the bottom of the heat exchanger sections is about 50 Cand at the top is about C.

What is claimed is:

1. An apparatus for producing cyanogen chloride comprising a source ofvaporized hydrogen cyanide mixed with gaseous chlorine, a hollow spraychamber having a gas dispersing means for conveying the mixture ofhydrogen cyanide vapor and chlorine to said dispersing means from whichthe mixture is sprayed into said spray chamber toward the spray of themixture, water supply means connected to said water nozzle means forsupplying water under pressure to said nozzles, whereby a spray of wateris directed into spray to spray contact with the spray of said mixture,a gas outlet meansnear the top of said spray chamber for removingcyanogen chloride and hydrochloric acid, respectively, a reaction columnhaving a heat exchanger therein with at least one tube therein, a

packed section above said heat exchanger and a packed section below saidheat exchanger, a line from said gas outlet means in said spray chamberto the lower packed section of said reaction column for feeding thegaseous reaction products from. said spray chamber to said reactioncolumn, gas outlet means at the top of said column, and liquid outletmeans at the bottom of said column for removing cyanogen chloride andhydrochloric acid, respectively, and a reboiler connected to the liquidoutlet means of said spray chamber, said reboiler having a gas outletmeans and a liquid outlet means, the gas outlet means of said reboilerbeing connected to said line to said lower packed section and saidliquid outlet means being connected to the top of said upper packedsection of said reaction column, whereby the hydrochloric acid from thebottom of said spray chamber is stripped of chlorine in the reboiler,the chlorine being fed to the lower part of the reaction column with thecyanogen

